The present invention relates to a magnetic recording medium, and particularly to a magnetic recording medium having excellent wear resistance that can be used for magnetic disks, floppy disks, magnetic tapes and magnetic cards.
Magnetic recording media usually consist of a magnetic film applied onto substrates of a variety of types. At the time of recording and reproducing the data, the surface of the magnetic film is rubbed with the magnetic head. Therefore, the magnetic film is worn out causing the properties thereof to be seriously deteriorated.
So far, therefore, it has been widely attempted to apply a lubricant onto the surface of the magnetic film in order to improve wear resistance. As the lubricant, use can be made of a silicone oil, higher fatty acid, higher fatty acid ester, higher fatty acid salt, or an organic fluorine compound such as perfluoropolyether. Amon them, the perfluoropolyether which is a fluorinated lubricant has been known because of its relatively excellent properties. For instance, U.S. Pat. No. 3,778,308 discloses the perfluoropolyether as a desirable lubricant for the magnetic recording media. In recent years, furthermore, there has been proposed a lubricant in which the terminal structure of the perfluoropolyether is improved. There has, for example, been known a perfluoropolyether having a polar terminal group as disclosed in U.S. Pat. No. 3,847,978. Furthermore, it has been proposed to apply the perfluoropolyether having the polar terminal group to the magnetic recording media, i.e., to use it as a lubricant that can be cleaned with isopropyl alcohol and that adheres well to the magnetic recording media (U.S. Pat. No. 4,268,556).
According to the above-mentioned conventional art, however, a single lubricant is simply applied without giving much attention to the structure of the lubricating film. Therefore, the wear resistance is improved to some extent but not to a satisfactory degree. At present, therefore, it is desired to further improve the wear resistance.
Furthermore, U.S. patent application Ser. Nos. 795,261 now U.S. Pat. No. 4,692,378 and 904,403 that are still pending and not published describe the application of perfluoropolyether to the magnetic recording media.